Ludy Bahneman

So I have a JDM 93 FD rx7, I recently rebuild the engine using an Atkins rebuild kit and also did a mild Streetport. After the rebuild one of my CAS connectors was bad so I replaced it and the car started up no problem. The second day I came back and was running the car to burn off all the Rebuild fluids when it died suddenly. I cranked and cranked and it wouldn't start, Its been 2 months since I had it running and I cannot find the problem. I even took it to a rotary shop and they found one the ignition harness was bad and I was getting spark to only 1 rotor. They replaced it and I am now getting very good spark. I have also replaced the Primary Injectors with good used ones because 1 of them was not spraying. The car will still not start for some reason, and I have checked the compression twice and it is good in both rotors. I even towed the car and had my buddy get up to 60 kph and I put it into second gear, the car backfires and stutters very badly but will not go on its own. I tried starter fluid and it sort of starts under WOT but sounds very rough and dies almost immediately after I let off the throttle. Only things I have not checked yet is the Fuel pump, and the volts going to the injectors. I also replaced the Coolant sensors just in case that had something to do with it. I am running an Apexi FC and have a few more mods on the car. It has no AC and no Power Steering, still on the stock twins, HKS intakes, Downpipe, no Cat, and has Simplified Vacuum lines. Any ideas or suggestions would help GREATLY, I am totally lost on why the car won't run as it ran beautifully before.

Akagis_white_comet

iTrader: (4)

I'm not sure if Japan-spec Series 6 FDs have the Fuel Pump Resistor on them, but checking voltage at the pump connector and injectors is a good idea. Does the car have other symptoms in seemingly non-related areas such as dim lights, sluggish blower motor, etc? If so, it would be indicative of poor grounds. Your ECU ground is on the shortblock and if it is poor, all of its signals will be skewed AWAY from ground. This throws off stuff like the TPS (a 0-5v voltage divider, 5v is WOT), making it believe you are giving it more throttle than it is actually receiving. The Map sensor works the same, a poor ground will skew its reading HIGHER (reading more pressure than what it is actually seeing). ECU responds to this by adding fuel and car runs like poopy due to poor injector/ignition signal (can't supply a clean signal to trigger injectors or coils properly).

Here is Aaron Cake's guide to grounds, he explains it far better than I could: Proper RX-7 Grounding Procedures

My fiancee's Ford Escort was behaving like its alternator had given out and battery was weak, while turning on the headlights completely killed it twice while driving. Towed it home, checked the grounds under the hood and they were shot. 1.7 ohms on the main ground cable (engine-body-battery negative) and 1.8-2.0 ohms on most of the grounds under the hood. The worst offender was located under the battery tray, 3.2 ohms and its bolt promptly broke when attempting to remove. Rehabbed all of them per Aaron Cake's article, soldered fresh ground cables and reinstalled. Car was instantly happy again.

Ludy Bahneman

[QUOTE=Akagis_white_comet;12280028]I'm not sure if Japan-spec Series 6 FDs have the Fuel Pump Resistor on them, but checking voltage at the pump connector and injectors is a good idea. Does the car have other symptoms in seemingly non-related areas such as dim lights, sluggish blower motor, etc? If so, it would be indicative of poor grounds. Your ECU ground is on the shortblock and if it is poor, all of its signals will be skewed AWAY from ground. This throws off stuff like the TPS (a 0-5v voltage divider, 5v is WOT), making it believe you are giving it more throttle than it is actually receiving. The Map sensor works the same, a poor ground will skew its reading HIGHER (reading more pressure than what it is actually seeing). ECU responds to this by adding fuel and car runs like poopy due to poor injector/ignition signal (can't supply a clean signal to trigger injectors or coils properly).

The car sometimes does have a very slow cranking rpms, but the lights don't seem to dim I don't think so. Originally it did seem like the car was flooding itself and I had to keep deflooding it.

TomU

iTrader: (11)

So an engine needs three basic things to start - compression, fuel, and spark (at the right time). Sounds like you have good compression. To check spark, you can pull the plugs and ground them against the engine and see if they spark when you crank it. That won't check timing though. The timing won't go out like a piston engine, but if your CAS isn't working right, it may affect timing. For fuel you can tee in a fuel pressure tester in the rubber line just before it connects to the hard line that goes under the UIM. That won't tell you if your injectors are working but will tell you if you have fuel at that point. If you have fuel pressure and spark, it could be either your injectors or your CAS.

If you are flooding, that means you are getting fuel in the engine, but it's not igniting. If you are cranking it and it won't start you are going to flood the engine (if your fuel system is working correctly). If you crank it a lot and then pull the plugs, they should be wet with gas if flooded. If they are dry, that might be an indication you're not getting fuel

Also, if it is starting with starting fluid and then dies, that generally means it's getting spark, but not getting fuel.

Start testing for fuel and spark and work backwards from there

Good luck